Resistive switching effect in thin-film heterojunctions based on electron-doped Nd2 ? xCexCuO4 ? y superconductor

Thin-film heterojunctions Nd_{2 − x} Ce _x CuO_{4 − y} /Ag were obtained. The bipolar effect of resistive switching in these heterostructures was detected and investigated. X-ray diffraction data indicate the presence of a second phase in thin films; along with the basic phase Nd_{2 − x} Ce _x CuO_{4 − y} , it affects the behavior of the interface of investigated heterojunctions and leads to an alteration of the type of conductivity. The threshold frequency of alternating voltage at which the resistive switching effect is observed in heterojunctions was detected.     

Control of morphology and dopant distribution in yttrium-doped ceria nanoparticles

The morphology and distribution of dopant in yttrium-doped ceria (YDC) nanoparticles prepared by spray pyrolysis were characterised by transmission electron microscopy and X-ray energy dispersive spectroscopy (XEDS), respectively. By combining the XEDS analysis and concentration distribution modelling, accurate yttrium dopant concentration variation from the particle center to the surface can be determined. It is shown that by appropriately selecting cerium precursors, the yttrium dopant distribution in YDC nanoparticles can be controlled. Uniform yttrium distribution in the YDC particles has been achieved, which is important to decrease probability of yttrium cluster segregation to improve oxygen ion conductivity in solid oxide fuel cell electrolytes. This control is based on the suggested mechanism of dopant distribution which proposes that hydration energies influence diffusion rates of the precursors during preparation process. In addition, the morphology (solid spherical, hollow spherical and hollow concave) formation mechanisms of the YDC particles from different cerium precursors are discussed.     

Photochemical synthesis of phosphinolines from phosphonium-iodonium ylides

We describe three different series of experiments which were undertaken to test our hypothesis that during irradiation of phosphonium-iodonium ylides (1a, 1b) an electrophilic carbene is generated. By opposing the assumed intermediate to monosubstituted alkynes, we observed in the case of electron-rich substituents at the triple bond a domination of a 1,3-dipolar cycloaddition of the intermediate with the triple bond to yield furans. In the case of electron poorer substituents, the formation of phosphinolines prevails. A second series of experiments was carried out with mixed ylides in which one phenyl ring at the triarylphosphonium group was replaced by a thienyl group. In this case, we observe only an intramolecular reaction with the thienyl ring to yield the phosphinolines 21-23. In a third test, we replaced in the mixed ylides 1a, 1b the COR group by a CN substituent. This modification leads to phosphinolines only and avoids a 1,3-dipolar cycloaddition.     

Spectral and Energy Data for Bis (Polyfluoro-Aryl) Amine Complexes with Hydrogen NH…B Bond

In the IR spectra of complexes of (C₆F₅)₂NH, (4-CF₃C₆F₄)₂NH and (γ-NC₅F₄)₂NH with acetonitrile, tetrahydrofurane, dimethylformamide, dimethylsulfoxide and hexametapole, the v(NH) band has a complex structure due to Fermi resonance with low-frequency vibration combinations. In the range of 15–65°C the equilibrium constants and complex formation enthalpies in CCl₄ solution have been determined.     

Electron transport in manganite bicrystal junctions

The transport and magnetic properties of junctions created in La_0.67Sr_0.33MnO₃ thin films epitaxially grown on substrates with a bicrystal boundary have been investigated. In tilted neodymium gallate bicrystal substrates, the NdGaO₃(110) planes are inclined at angles of 12° and 38°. The temperature dependences of the electrical resistance, magnetoresistance, and differential conductance of the junctions at different voltages have been measured and analyzed. It has been found that the magnetoresistance and electrical resistance of the junction significantly increase with an increase in the misorientation angle, even though the misorientation of the easy magnetization axes remains nearly unchanged. The ratio of the spin-dependent and spin-independent contributions to the conductance of the bicrystal junction increases by almost an order of magnitude with an increase in the misorientation angle from 12° to 38°. The magnetoresistance of the junction increases with decreasing temperature, which is most likely associated with an increase of the magnetic polarization of the electrons. It has been shown that, at low (liquid-helium) temperatures, the conductance depends on the voltage V according to the law V ^1/2, which indicates the dominant contribution from the electron-electron interaction to the electrical resistance of the junction. An increase in the temperature leads to a decrease in this contribution and an increase in the contribution proportional to V ^3/2, which is characteristic of the mechanism involving inelastic spin scattering by surface antiferromagnetic magnons.     

Physicochemical properties of a new group of regulatory proteins isolated from various mammal tissues

Russian Chemical Bulletin - The found similarity of the set of physicochemical characteristics of regulatory proteins active in microdoses isolated from various mammal tissues allows them to be...     

Anomalous enhancement of the coupling to the magnetic resonance mode in underdoped Pb-Bi2212

High-resolution angle-resolved photoemission with variable excitation energies is used to disentangle bilayer splitting effects and intrinsic (self-energy) effects in the electronic spectral function near the (pi,0) point of differently doped (Pb,Bi)(2)Sr(2)CaCu(2)O(8+delta). In contrast to overdoped samples, where intrinsic effects at the (pi,0) point are virtually absent, we find in underdoped samples intrinsic effects in the superconducting-state (pi,0) spectra of the antibonding band. This intrinsic effect is present only below the critical temperature and weakens considerably with doping. Our results give strong support for models which involve a strong coupling of electronic excitations with the resonance mode seen in inelastic neutron scattering experiments.     

Optical Properties of Semiconducting Ruthenium Silicide

The optical properties of ruthenium silicide Ru₂Si₃ have been studied theoretically and experimentally. The energy band spectrum and optical properties were simulated with the aid of the firstprinciple selfconsistent method of linear attached plane waves. The spectral dependence of the absorption coefficient in the 0.52.2 eV energy range was measured experimentally by the photothermal refractive spectroscopy method. It is established that ruthenium silicide is a directgap semiconductor having an energy gap of 0.84 eV and a low oscillator strength of the first direct transition.